tech tach query

Gage going out, Break in the line, sensor going out.

 

Call Pererbilt maybe?
or
pull the Tach check the connections then craw under the truck and check the connectors at the tail sensor.That' s all you can do except to "buy" either a new Tach or sensor. Best thing is to hit the dealer and let them put the computer on it. You won't find a bad cable with the tools you have and telling if a sensor is out if it doesn't show on your dash "flash codes" is something which is a heck of a lot cheaper letting the shop find! These new trucks don't use a wheel sensor anymore and haven't for years! Your time you spend looking for a problem will cost more than letting a shop do all that electrical work and if you don't know what you're doing on any type of truck problem the extra OJT costs will teach you that lesson really fast if you can handle that type of learning curve! This ain't 60's 70's and 80's technology any more! It's just like that new car sitting in your driveway. You don't have the programs on your laptop to work on it! No more shade tree mechanicing these days!

I'll still go with "Call the Dealer"!